This invention relates generally to nebulizers for use in respiratory therapy and more specifically to nebulizer systems which include a flexible reservoir for retaining nebulized aerosols between patient inhalations.
In the field of respiratory therapy, it is sometimes desired to provide a patient with a medication that has been disbursed into very small particles using a nebulizer. In such therapies, a patient typically breaths the nebulized air through a mouthpiece and exhales through the same mouthpiece. The mouthpiece is generally connected to a manifold which includes both an inlet port and an outlet port. A nebulizer is typically in communication with the inlet port. Medicated aerosol thus enters the patient from the inlet port of the manifold. In most applications, the inlet port and the outlet port of the manifold are in fluid communication with one another. This allows any excess pressurized air coming from the nebulizer to be exhausted through the outlet port of the manifold when a patient is not inhaling. One problem with such a system is that is inefficient in that it allows medicated aerosol to be lost.
One method for overcoming this problem has been to include a rigid chamber for receiving excess medicated aerosol from the nebulizer when the patient is not inhaling. Typically, this rigid chamber may also include a one-way valve which serves to prevent aerosol from flowing out into the room. However, if the rate in which a patient is inhaling is greater than the flow rate the nebulizer, the one-way valve allows room air to enter the aerosol delivery system to make up for the deficiency in flow rate from the nebulizer. Accordingly, air flowing through this valve is commonly called "make-up room air". Since make-up room air typically flows through the rigid chamber during patient inhalations, the chamber remains essentially full at all times. Accordingly, in between patient inhalations, it has been found that only a small percentage of medicated aerosol actually enters the rigid chamber rather than exiting the system by flowing through the manifold to the outlet port.
One of the problems with respiratory therapy systems that include a rigid chamber as described above is that is can be undesirably expensive to provide certain medications to a patient. For instance, pentamidine isethionate is a relatively expensive drug that is currently being administered as a small-particle aerosol to patients having Pneumosystis carinii pneumonia. Currently, the cost of administering this medication to a patient may be as much as $200 per treatment. If a system can be developed which is 50 percent more efficient in administering the medication to a patient, the cost of the medication can be reduced by 50 percent.
Another problem with administering an aerosol in which large portions of the aerosol are not inhaled by a patient is that is can be difficult to determine how much medication a patient has actually received during an individual treatment. If it is possible to efficiently collect the aerosol between inhalations and use that aerosol (rather than make-up room air) during subsequent inhalations, the amount of medication actually received by a patient may be more accurately estimated.
Yet another problem with systems in which an aerosol is inefficiently administered to a patient is that the treatment time is directly related to the efficiency of the aerosol delivery system. This problem is particularly acute when it is necessary to deliver the medication as a small particle aerosol. For purposes of this application, small particles are considered to be in the range of 0.3 to 2.0 microns. Currently, only a small amount of drug is available during each inhalation because it is limited by the amount that can be nebulized during that inhalation time. By providing a system which can efficiently collect and store medicated aerosol between inhalations and add that aerosol to aerosol being generated during a patient's inhalation, it is possible to increase the mass of drug inhaled during each inhalation.
Therefore, a need existed to develop a system for efficiently and effectively collecting small particle aerosols between patient inhalations and delivering such collected aerosol to patients during the next inhalation.
A need also existed to develop an increased efficiency aerosol delivery system which capable of being manufactured at a relatively low cost.
A need also existed to develop an increased efficiency aerosol delivery system which could be easily tolerated by a patient during use.
These and other needs have each been met by the device described below.